The present invention relates generally to tub and frame assemblies for front loading appliances. More specifically, the invention relates to front loading dishwashers incorporating molded plastic tubs.
Front loading dishwashers incorporating molded plastic tubs are presently commercially available. Exemplary dishwashers of this type are illustrated and described in commonly-assigned U.S. Pat. Nos. 3,826,553 and 3,811,746.
The advantages of using a one-piece plastic dishwasher tub rather than a metal tub are numerous. For example, cost factors are greatly decreased in the manufacture of a molded plastic tub as compared to those involved in the manufacture of a metal tub, which requires an inner coating or lining operation. Other advantages include a reduction in finishing labor requirements, particularly tub welding operations, a longer tub life due to corrosion resistance which is independent of faulty coating procedures or chipping, and a decrease in thermal and acoustical transmission which minimizes the need for separate heat and sound insulation.
However, plastic tubs tend to deform. Deformation may occur when the tub is subjected to the high normal operating temperatures in a dishwasher, such as to approximately 180.degree. F. Deformation may also occur when the tub is subjected to various loading forces, such as the weight of the dishwasher itself when placed on an uneven flow. Such deformation is undesirable and should be prevented for several reasons. It is particularly important that the original cross sectional rectangular shape of the tub be maintained in order for the swing-down door on a front-loading dishwasher to maintain a proper water seal to prevent leakage. Additionally, dish racks are usually mounted to slide in and out of the dishwasher, an action which would be inhibited by tub deformation. Further, if a tub deforms under heat or load forces its appearance or "feel" of quality is reduced.
To combat deformation problems, the dishwashers described in the aforementioned patents employ a relatively substantial box-like metallic base and a relatively substantial metallic collar placed around the tub. While this arrangement satisfactorily controls tub deformation and provides significant material and labor cost savings over metallic tub arrangements, the collar and base are relatively structurally complex, employ a significant amount of steel, and require significant labor time in assembly.
It is desirable to provide a tub assembly for a plastic tub which retains the structural rigidity provided by a steel frame, but which employs significantly less steel than prior art arrangements and which is less complex to assemble.
Therefore, it is an object of the present invention to provide a tub assembly incorporating a plastic tub for a front loading washing appliance which retains the structural advantages of the steel frame while employing substantially less steel, thereby reducing material costs, and which involves a greatly simplified configuration, facilitating assembly and reducing labor costs.